[plug] anti-spam + postfix

[Craig Ringer]

> Any suggestions for overcoming this problem?  I have considered just 
> removing the ISP relay server as a backup mx, but thats really not 
> desirable or practical at all....

The only one I can suggest is find someone else you can use as a backup 
MX - who will run an RBL. If you're really desparate, you could always 
set up your own backup MX as a co-lo.

On a superficial examination, I'd be extremely reluctant to do any kind 
of Recieved: header checks since those headers are so easily spoofed 
(adding history that did not happen before the first real transmission). 
OTOH, I suppose it's only going to be spoofed by those who are spamming 
you, and they'll still appear on the list anyway. There's no reason for 
a legit transmission to add a fake entry in the Recieved: headers (and 
if they do for some incomprehensible reason fake a path from an open 
relay or spammer, good riddance to them).

Perhaps either solution could work out well.

Craig Ringer